Normally I would not subscribe to such beliefs, however, recently I picked up a pendulum from a shop and could swear I witnessed a piece of my consciousness enter the stone.
The only thing I can think of that I am aware of is a soul retrieval, but be cautious whom you ask to help with this.
There are a number of frauds whom claim to have experience with such things.
There are also methods you can try yourself. One does this by journeying in mind's eye to retrieve the piece of themselves.
It would be of greater benefit to you, I feel, to try this on your own as to not be taken for a ride.
But, in all honesty if you are not experiencing any unpleasant effects currently, it may be best to relax. You may not need actively do anything for this at all.
I think some additional details would be helpful, as such an event is very unusual to encounter. The concept of soul is that of the continuous and enduring nature of one's identity and consciousness. While energy is a large component of the presence of a person's soul, it doesn't define the strength or nature of it. Quite the opposite actually. It is the nature and quality of the consciousness that builds and defines the energy it presents. To lose a genuine part of one's soul would be akin to removing a portion of someone's thoughts and identity. A removal of memory, goals, ability of reason, spiritual connection and capability. You wouldn't be 'weaker' so much as definitively lesser/reduced at the core of your being.
Loss/movement of energy is much more likely, and also much less to worry about. One's energy comes and goes as fluidly as breath from the lungs. Or, like water from a lake if you prefer. You can starve yourself of energy by putting out too large an amount without being prepared, or by consistently putting out more energy (focus, effort, emotion, activity, etc) than you are able to regain (nutrition, rest, proper breathing, meditation, etc). Moments of imbalance are normal, and self-correcting over time. ...Helped along through attentiveness and self-care, of course.
Sudden, massive loss or expenditure of energy is less common, but does happen for a variety of reasons. High emotional stress, major illness, severe lack of rest, and spiritual attack among them. The first step to reclaiming/replenishing spent energy lies in seeking an understanding of what caused it in the first place. If you can give more information on what happened, it should help give some insight for more specific advice.
